This paper proposes a continuous real-time structural health monitoring (SHM) and damage detection system. Wavelet
packet decomposition (WPD) with a likelihood ratio was used for the damage sensitive indicator (DSI). A benchmark model updating structure instrumented with acceleration sensors was used for demonstration tests. A real-time reference-free damage detection algorithm is successfully implemented and verified using the benchmark test structure. The DSI based on WPD with a likelihood ratio algorithm showed consistency with two different damage scenarios. Furthermore, the application was web-published on a remote collaboratory site for remote access to a real-time structural health monitoring system.
In this paper, a wavelet entropy based damage identification method is experimentally validated using wireless smart
sensor units (Imote2) with TinyOS-based firmware. Recently, the wireless smart sensor network has drawn significant
attention for applications in Structural Health Monitoring (SHM). Wavelet entropy is considered to be a damagesensitive
signature that can be obtained both at different spatial locations and time stations to indicate changes in
dynamic responses of structures. Compared to metrics based on the Fourier Transform, metrics based on wavelets
require much simpler mathematics, with no complex numbers. Thus wavelet-based SHM methods would be easier to
embed on motes. Wavelets can have other (mathematical) advantages when the structures are complex and the dynamic
signals are non-stationary. Particularly, use of the relative wavelet entropy (RWE) has been extensively explored for use
in damage detection using wireless smart sensors. First, sensor validation tests have been conducted using wireless and
wired sensors. To verify an off-line time synchronization technique and the feasibility of using acceleration data from
wireless sensors, modal identifications have been conducted using the ERA technique. Finally, the wavelet entropy
based damage detection method has been demonstrated using Imote2 wireless smart sensors.